JUST how accurate is that step-counting, staircase-scoring, calorie-calculating bracelet on your wrist?

Fitness gadgets like the Samsung Gear Fit and Jawbone Up24 are skyrocketing in popularity as part of the multi-billion-dollar wearable technology market.

Consumers are expected to splash $19 billion on wearable gadgets within four years, according to Juniper Research, with $1.4 billion spent last year alone.

But popularity does not equal accuracy.

While these fitness gadgets promise to count every step you take, and monitor your heart rate, floors climbed, and distance travelled, they can deliver very different results.

To rate their accuracy, we strapped on eight fresh fitness gadgets for the 15km Kokoda Challenge hike. Six of the devices were worn on our left and right arms, while one was strapped to a waistband, and another carried in a pocket.

Despite claims of accuracy, the devices delivered discrepancies as large as 9,151 steps, 5.48km, and 19 floors over the course of the hike.

The Samsung Gear Fit performed well.Source:Supplied

One popular smartwatch quickly proved the most unreliable of the bunch.

Registering just 17,916 steps over the 15km hike, the Pebble Steel was downright unreliable.

The watch features a 3D accelerometer that, when used with the Pedometer app from its store, is designed to register steps. Sadly, we watched its black and white screen as it failed to recognise each step on the hike, sometimes counting one in two steps, and thoroughly failing the accuracy test.

Similarly, the Sony SmartBand malfunctioned as it failed to register more than 209 steps.

On the other end of the scale, a top five was obvious. Fitness devices from Samsung, Jawbone, Withings, Fitbit and even the humble iPod Nano showed a difference of just 499 steps.

The difference between the two most sensitive gadgets, the Samsung Gear Fit and Jawbone Up 24 — also the most recent and two of the most expensive of the competition — was tiny by comparison at just 65 steps.

The Jawbone Up24 kept good pace.Source:Supplied

The pair counted about 27,000 steps each, a tally reflected by the ache in the wearer’s legs, and proof some fitness gadgets do get it roughly correct.

But even the best step-counters disagreed when it came to distance travelled.

Each device is programmed to give its own estimate of step size, with some basing calculations on the wearer’s height, weight and age to guess their gait.

Even those which did use the user’s information, including the Apple iPod Nano, delivered very different results.

A significant gap of 5.48km emerged between the Misfit Shine and Apple’s iPod Nano, which estimated it had covered almost 22km during a 15km hike.

While it’s difficult to say which device is the most accurate, the iPod and Withings Pulse estimates of more than 21km seem hard to believe.

The wildly different distance estimates may have been affected by steep hills on the Brisbane Forest Park track.

The Fitbit Force and Withings Pulse gauge a user’s ascent using altimeters, though at 3m per floor, the pair disagreed by approximately 19 floors.